1. Field of the Invention
The present invention relates to an information recording medium which comprises a defect management area for storing defect management information. The present invention also relates to an information reproduction apparatus and information reproduction method for reproducing user data by acquiring defect management information from an information recording medium. The present invention further relates to an information recording method for recording defect information on an information recording medium.
2. Description of the Related Art
An information storage medium such as an optical disk has a user area used to store user data, and has a mechanism for compensating for defects generated in this user area. Such mechanism is called a replacement process. An area that manages information associated with this replacement process, i.e., defect management information, is called a DMA (Defect Management Area).
Of information recording media, a DVD-RAM allows 100,000 or more overwrite accesses. Even when the DMA of such medium with very high overwrite durability undergoes tens of thousands of overwrite accesses, the reliability of the DMA does not drop.
For example, Jpn. Pat. Appln. KOKAI Publication No. 9-213011 discloses a technique for improving the DMA reliability by allocating a plurality of DMAs on an optical disk.
However, in the case of an information recording media having a relatively small allowable overwrite count (several ten to several thousand times), overwrite accesses to a DMA of such a medium poses a problem. That is, the DMA of such a medium is easily damaged by overwrite accesses.
This problem cannot be solved even by the technique disclosed in Jpn. Pat. Appln. KOKAI Publication No. 9-213011. That is, even when a plurality of DMAs are allocated, since respective DMAs undergo overwrite accesses at the same time, if one DMA is damaged by overwrite accesses, other DMAs are also damaged.
Each DMA stores defect management information, as described above, and if the DMA is damaged, defect management information cannot be read out from the DMA. As a result, the medium itself can no longer be used. Hence, it is demanded to improve the overwrite durability of the DMA.